Sheet detector



April 10, 1945.

H. BOBST SHEET DETECTOR Filed Sept. 17, 1941 all/II .i aiii zi INVENTOR- HENRI BOBST Bv zlnw q/afl ATTORNEYS Patented Apr. 10, 1945.

. UNITED STATES PATENT OFFICE SHEET DETECTOR Henri Bobst,'L ansanne, Switzerland Application 4 Claims.

It is known to dispose in automatically working machines for feeding blanks, controllers to ensure for example electro-magnetically the feeding of blanks one at a time, said mechanisms stopping the feeder a soon as two superimposed blanks are fed together.

In automatic stackers the overlapping blanks do not permit an exact gauging so that the presence of a supplementary sheet cannot be revealed positively. V

The known gauging mechanisms further are not precise or involve heavy or encumbering devices. In the usual blank feeders, the gauge is commonly disposed in the passageway of the blanks, near the middle part of it and just after they have left the pile, in order to be able to control as well blanks of a large size as blanks .of a small size. Due to the fact that a part of the mechanism must be placed under the sheets and another part over the sheets, the slight flexnre of the bearings erves to make a precise measure impossible. In order. to avoid these inconveniences, the measures are made each time when the machine does not vibrate or by means of jawshaped gauges of a large size, permittin the passage of large blanks.

According to the present process, the gauging takes place near the edge of the stacked blanks and near the front registering marks, each time when a single thickness of cardboard passes where the gauging operation is made.

The drawing shows an embodiment of an apparatus for executing said process.

Fig. l is a side view showing the extremity of stacked blanks and the apparatus.

Fig. 2 shows said apparatus on a larger scale, part in cross-section, the blanks being intended to travel in a direction front to back perpendicular to the plane of the drawing.

Fig. 3 is a front view of the apparatus on the same scale as in Fig. 2.

Fig. 4 is a cross-section along the line IV-IV of Fig. 2.

In Fig. 1, the stacked blank I, 2, 3 and 4' come from the right in direction of arrow 5.

They are conveyed by bands 6 passing over pulleys I.

As the blanks are stacked, the front edge of blank I is free and reaches alone the front registering marks at proximity of which there is therefore only one thickness of cardboard. This matter of fact is only momentary, it lasts practically during the time when the considered sheet is registered partly against the marks 8 in the direction of feeding and partly against the lat- September 17, 1941, Serial No. 411.144 Switzerland October 10, 1940 the lateral abutment 9.

eral abutment 9, to be seen at Fig. 2, in the transverse direction. Immediately after that, the sheet is seized by the parts of a machine, not to be seen here, in which said sheet is worked. While the latter enters into the machine, the sheet 2 that follows it goes forward as well, and there are soon two sheets superimposed at the place where sheet number i only showed a single thickness before.

It is at that place and at the exact moment when possible to measure a single thickness that an apparatu of ,control designated by in in Fig. 1 will be able to measure with all the precision needed and this much more due to the fact that the apparatus is movable in the transverse direction, and it will alway be driven to the edge of the sheet and will avoid the necessity of having a deep jaw-shaped device, cause of inaccuracy. As the details of Fig. 2 show, the apparatus I0 is made of a frame I, supporting a case whose height is skillfully regulated and comes above the passage of sheets. Said case contains a freely hanging lever l2, under which and in relation to which a small roller I3 is raised and lowered, being able to draw near at such a distance that between the roller and the levers base remains only a space hardly greater than to a sheet's thickness. Fig. 2 shows the small roller out of action, i. e. distant from the lever base, and Fig. 3 shows it working, i. e. in the position of measuring. These two positions are obtained by rocking of lever l4, operated by a cam 15, to be seen in the cross-section of Fig. 4. Said cam is driven by a toothed-wheel l6, from a driving shaft l1, placed transverse to feeding directiomand havnig a key-way l8 making it possible to remove the whole apparatus In in the two directions indicated by the arrows l9, with regards to the wideness of sheets that must be controlled.

This removing is even more important because of the fact that the apparatus of control supports the lateral abutment 9, in a position skilfully regulated with a screw 20. To register the sheets laterally, the apparatus has besides that two friction pulleys 2|, 22 of which the pulley 2|, driven in the direction shown by an arrow, comes under the sheet to be controlled, while the pulley 22, Fig. 2., shown in working position, comes above, but can be lifted to allow the passage of sheets. In working position of pulley 22 the pulleys 2|, 22 tend to pull sheets by side against The raising of pulley 22 against the action of a regulable spring 23 is made with the aid of a second cam 26, to be seen at Fig. 4, and working on lever 2! bearing said pulley.

The lever i2 supports a mercury-switch 28 intended to close a stopping circuit of the stacker as soon as said lever moves when more than one sheet at a time passes through.

Thi is now how the described mechanism operates to work the claimed process:

When the stacked sheets move and the top sheet for example the one lying on the sheet I was Just introduced in the machine not shown and placed onthe left, close to the stacker, the cam It raises the roller it. This operation must take place exactly between the moment when the said sheet has been taken away and when the next sheet has not yet reached the marks I, but gets near, because in case of error, it is necessary that a movement could be communicated to the lever I! in order to rock the said lever and stop the stacker as soon as the measured thickness exceeds that 01 a single sheet. 7

As soon as the measured sheet reaches the marks 8 and stops there or just before its stop, the roller I3 lowers in resting position and the pulley 22 in working position that provokes the lateral sliding of the sheet against the abutment 9. Then the sheet is entirely registered.

These operations begin again on the passage of each sheet and as long as everything works normally.

n the contrary,.if two sheets cross simultaneously the controls apparatus I 0, it is quite evident that the overthickness given will provoke the rocking or lever l2, serving to rock the mercuryswltch 28 which has the duty to stop immediately the function of the stacker.

Given that it merely nvolves always a short movement while the con rolled sheet is at stillstand in said position; it is possible then to check it with an appropriate gauge. On the other hand, it is also possible to control the sheets by means of a rocking lever placed across the feeding direction and efiecting the control operation when sheets are registered .laterally.

What I claim is:

1. In a machine having a trip device, a sheet detector for ensuring the delivery or feeding of but one sheet at a time from a supply of sheets being fed from a conveyor, including a driving shaft disposed on said machine in a transverse direction with respect the feeding direction of the sheets for imparting power to said detector, a detector frame mounted exclusively on said shaft to be measured, a second detector member pivotally mounted on said frame-above the sheet to be two detecting members, .and means operated by one of said detecting members for causing actuation of said trip device upon encounter of said one detecting member with more than a single sheet at said position.

2 A sheet detector according to claim 1, in which the second detecting member includes a swlngable pivoted lever and the first detecting member includes a pivoted arm carrying upon its extremity a roller for making contact with the under surface of a sheet, and wherein the shifting means includes a driven cam upon said frame serving periodically to lift said am and roller into active'position. I

3. A sheet detector according to claim 1, in which the second detecting member includes a swingable pivoted lever, an electric switch member operated by the second detecting member for actuating said trip device, and the first detectin member includes a pivoted arm carrying upon its extremity a roller under-surface of a sheet, and wherein the shifting means includes a driven cam upon said frame serving periodically to lift said arm and roller into active position.

4. A detector according to claim 1, in which the second detecting member includes a pivoted pendent lever swingable in the feeding direction,

' said lever being adapted upon swinging of same past normal pendent position by thickness than that of one sheet trip device.

a greater sheet to actuate said HENRI BOBST.

for making contact with the 

